Suspension device for tree felling unit

ABSTRACT

The invention relates to a crane-supported pivotal tree felling unit of the type at which gripping arms press the tree stem against a thrust on the unit whereafter the steam is cut by a cross cut member disposed below the gripping arms. In the final phase of the cross cutting operation the jib is lifted so that the breaking of the stem is facilitated by lever action, whereby the force-actuated end of the lever corresponds to the suspension point of the unit on the jib. According to the invention said suspension point is so movably connected with the unit by a linkage that at said lifting of the jib a spring means retaining the linkage is overcome and the suspension point is moved rearwards from the tree, thereby increasing the effective length of the lever and, thus, increasing correspondingly the breaking moment acting on the tree.

United States Patent Runeson SUSPENSION DEVICE FOR TREE FELLING UNIT Primary ExaminerGera.ld A. Dost Attorney-Pierce, Scheffler 8: Parker [72] inventor: Stig Olov Runeson, Alfta, Sweden ABSTRACT [73] Assignee: Ostbergs Fabrlks AB, Alfta,

Sweden The invention relates to a crane-supported pivotal tree felling unit of the type at which gripping arms press [22] Flled: the tree stern against a thrust on the unit whereafter [2| Appl 95,555 the steam is cut by a cross cut member disposed below the gripping arms. in the final phase of the cross cutting operation the lb is lifted so that the breaking [30] Foreign Amman. Horny of the stem is facilitated by lever action, whereby the Dec. 12,1969 Sweden ..172i8l69 force-actuated end of the lever corresponds to the suspension point of the unit on the jib. According to [52] [1.8. CI. R the iny enfion said suspension is so moyably con- [51 1 Int. Cl. A018 nected the unit a linkage that at of [58] FieldoiSearch.....l44/3 D, 34 R, 34 E, 309 AC the jib a Spring means retaining the linkage is oven come and the suspension point is moved rearwards [56] Refem cued from the tree, thereby increasing the effective length UNITED STATES PATENTS of the lever and, thus, increasing correspondingly the breaking moment acting on the tree. 3,565,141 2/1971 Gains ..144/34 R 6 Claims, 5 Drawing figures I ?P:" I I \L 7 -fi 2 i ,n 1 s 13 up '5 l u A -T 4 PNENTEB SE? 5 BR SHEETUBF! SUSPENSION DEVICE FOR TREE FELLING UNIT This invention relates to a suspension device for a tree felling unit of the type, which in a point above and substantially in the plumb line with the center of gravity of the unit is pivotally supported on a liftable and lowerable carrier means, such as a jib, and which is provided above its cross cutting member with gripping arms pivotally mounted for pressing the thrust plate of the unit against a tree stem during the cross cutting operation.

At units of the aforedescribed type it is possible, by designing the cross cutting member increasing in thickness from the working edge to form a wedge, to bring about a moment acting upon the stern during the cross cutting operation and thereby to effect a directed felling away from the unit. This wedge-shaped design, however, involves several disadvantages, the most significant of which is the friction caused by the keying force. Due to this friction, the cross cutting member requires with increasing stem dimension an increasing driving power.

The invention solves the problem of directed felling in a quite different way. For this purpose the unit is provided with a suspension device, which is characterized in that the movable point is located at one free end of an arm, the other end of which is pivotally mounted about a horizontal axle at the rear portion of the plate, and a spring means acting between the plate and the arm is adapted to press a stop surface on the arm against a stop surface on the plate, so that at a freely suspending unit the movable point is held substantially in the plumb line with the center of gravity of the unit, but that by lifting the carrier means, subsequent to the fixing of the unit at the stem by means of the gripping arms, the movable point by overcoming the force of the spring means is caused to participate in the upward swing of the arm to a position, for which the movable point is located substantially in the plumb line with the axle and thereby increases the effective lever of the carrier means so as in the final phase of the cross cutting operation to facilitate the breaking of the tree in the desired felling direction away from the unit.

The invention is described in greater detail in the following, with reference to the accompanying drawing, in which FIGS. 1 and 2 show in a schematic way a lateral and horizontal view, respectively, of a felling unit equipped with a suspension device according to the invention,

FIG. 3 shows on a smaller scale an alternative embodiment of the directive force means used at the invention, and

FIGS. 4 and 5 show the complete felling apparatus in a position before and during, respectively, the felling operation.

The tree felling unit proper is illustrated in the Figures only by way of the upper plate 1 for a frame, which encloses the cross cutting member, for example an endless saw chain, acting in the direction of the Arrow A, and which supports gripping arms located above the cross cutting member for embracing the stern in question and pressing the unit against the same.

T designates the plumb line through the center of gravity of the unit. A two-armed lever 2, 3 comprising two sheet metal legs (see FIG. 2 showing the arrangement being symmetrical about the line 0-0) is mounted about an axle 4, which extends through two upwardly directed ears 5 on the plate 1 near its rear end. Through a second pair of ears 6 projecting up wardly from the front portion of the plate 1 extends an axle 7, and through the end of the shorter arm 3 extends an axle 8. About the two axles 7 and 8, on each side of the lever 2, 3, are placed endless rubber belts l0 spaced by a set of apertured discs 9. At the forward portion of the arm 2, between its two legs, an axle 11 is mounted which serves as a point of engagement for a universal joint. Said joint in its turn is supported at the end of a jib or the like (for example via a rotator so that the unit is freely suspended. The rubber belts 10 are prestressed such that at the unit in suspended state the lower surface of the arm 2 is pressed against the upper surface of the plate 1. At this position, the suspension axle l l is in the plumb line with the center of gravity of the unit, i.e. the line T in the position of the lever 2, 3 shown by fully drawn lines.

Two links 12 and 13, which in FIG. 1 are merely indicated by their center line in order not to complicate the Figure, are at one end hinged with one another in the point 14 and at their other end mounted about an axle 15 between the legs of the arm 2 and, respectively, about the axle 7 in the ears 6. The object of this linkage is merely to act as a stop means, as will be explained later on.

H0. 3 shows an alternative to the directive force means formed by the rubber belts 10. The ear 6 has been replaced by an angular support 16, the upwardly directed front surface of which forms a stop for one end of a rubber hollow spring 17 drawn upon a rod 18 extending through the front surface of said support. The other end of the spring 17 abuts a stop washer 19 on the free end of the rod. At its other end the rod [8 is hinged via a link 20 with the axle 8 on the arm 3, which in this embodiment has a somewhat modified extension. By adjusting the nut 21 on the free end of the rod, the spring 17 can be compressed to effect the same prestressing of the lever 2, 3 against the surface of the plate 1 as the directive force means shown in FIGS. 1, 2, 4 and 5.

FIGS. 4 and 5 show the suspension device of the invention connected to a conventional rotator 22 which is, in its turn, suspended from the jib 23 via a universal joint 24. The stem of a tree to be felled is shown in FIG. 5.

The device shown in FIGS. 1 and 2 operates as follows. The unit freely pivoting about its suspension point 11, with its plumb line extending through the center of gravity of the unit, is moved against the tree to be felled, and by the aforementioned gripping arms (labeled 26 in FIGS. 4 and 5) engaging above the cross cutting member the unit (plate 1) is pressed against the stem whiie being maintained in a substantially horizontal position. Thereafter the cutting operation is commenced, for example by a saw chain 27, roughly indicated in phantom lines in FIG. 4 and operated by hydraulic means 28. Simultaneously, by a lifting of the jib 23 or a corresponding lifting means, the suspension point 11 is subjected to an upwardly drawing motion. The unit is retained clamped against the stem and, thus, the prestressing force of the rubber belts is overcome, and the lever 2, 3 is pivoted about the axle 4 to the position indicated in FIG. 1 by dash-dotted lines and in FIG. 5 in full line. In this position the suspension point 11 is substantially vertically above the pivot axle 4, and the linkage 12, 13 is straightened between the points 7 and 15 as indicated by double dash-dotted lines.

'Owing to the fact that the lever acting on the cutting line of the tree is extended from the engagement point located relatively closely to the forward edge of the unit above the center of gravity of the unit to a point nearer the rear edge of the unit, in the final phase of the cutting operation a correspondingly higher felling force and a well-defined felling direction are obtained. The bending moment, which during the entire cutting operation continuously is exerted on the stem portion above the cut, prevents effectively the cross cutting member 23 from being pinched. One should, furthermore, observe that an active contribution to a directed felling and gentle treatment of the surface wood exposed to break is rendered by the rapid rearward movement of the stem still retained by the gripping arms, which rapid movement is brought about by the return force of the rubber belts acting obliquely rearwardly upwardly on the unit.

The aforementioned linkage l2, l3 prevents the suspension device, and particularly the rubber belts, from being subjected to too heavy stresses in connection with the falling of the tree, because the extended links form a stop to the pivotal movement of the lever 2, 3 beyond the position indicated by dash-dotted lines in relation to the unit.

The conditions are analogous when using the device with a compressible rubber hollow spring shown in FIG. 3. In that case the said stop can be obtained by a suitable choice of the maximum compression limit of the spring. In both cases, furthermore, the directive force means has a dampening effect on the swinging of the unit between its movements.

The invention is not restricted to the embodiments shown, but wide variations can be imagined within its scope, particularly with respect to the directive force means and the stop means. Instead of the rubber belts shown and the rubber hollow springs, tension or compression springs of a more conventional type or torsion springs can be used. It is thinkable in principle also to exchange the lever mounted at the rear portion of the unit against some other means for effecting the desired movement of the suspension point rearwardly in relation to the plumb line through the center of gravity of the unit.

What I claim is:

1. Suspension device for tree felling unit, which in a point above and substantially in the plumb line with the center of gravity of the unit is pivotally supported on a liftable and lowerable carrier means, such as a jib, and

which is provided above its cross cutting member with gripping arms pivotally mounted for pressing a thrust plate of the unit against a tree stem during its cross cutting, characterized in that the movable point is located at one free end of an arm, the other end of which is pivotally mounted about a horizontal axle at the rear portion of the plate and a spring means acting between the plate and the arm is adapted to press a stop surface on the arm against a stop surface on the plate, so that at a freely suspending unit the movable point is held substantially in the plumb line with the center of gravity of the unit, but that by lifting the carrier means,

s bseq nt t th fixi f th t t te b nieans (if the gripging a ris jthe i n a bl po ir it y ve coming the force of the spring means is caused to participate in the upward swing of the arm to a position, for which the movable point is located substantially in the plumb line with the axle and thereby increases the effective lever of the carrier means so as in the final phase of the cross cutting operation to facilitate the breaking of the tree in the desired felling direction away from the unit.

2. Suspension device according to claim 1, characterized in that a second arm upwardly inclined relative to the first arm is rigidly connected to the mounting end of said first arm, and that the spring means is mounted between the outer end of said second arm and a holding means on the plate movable in. the forward direction of the unit relative to the axle.

3. Suspension device according to claim 2, characterized in that the spring means comprises at least one tension spring, one rubber belt or the like, and that the holding means is located substantially above the center of gravity of the unit.

4. Suspension device according to claim 2, characterized in that the spring means comprises at least one compression spring or rubber hollow spring, which with its end remote from the axle abuts an end stop on a rod extending through said spring and with its other end abuts a holding means through which said rod projects and is hinged at its end with the outer end of said second arm via a link.

5. Suspension device according to claim 1 characterized in that it comprises a stop means preventing at the felling of the tree the movable point from moving with its plumb line past the axle.

6. Suspension device according to claim 5, characterized in that the stop means comprises a hinged link or chain engaging between a forward point on the unit, preferably near the holder, and a place on the first arm, preferably near the movable point. 

1. Suspension device for tree felling unit, which in a point above and substantially in the plumb line with the center of gravity of the unit is pivotally supported on a liftable and lowerable carrier means, such as a jib, and which is provided above its cross cutting member with gripping arms pivotally mounted for pressing a thrust plate of the unit against a tree stem during its cross cutting, characterized in that the movable point is located at one free end of an arm, the other end of which is pivotally mounted about a horizontal axle at the rear portion of the plate and a spring means acting between the plate and the arm is adapted to press a stop surface on the arm against a stop surface on the plate, so that at a freely suspending unit the movable point is held substantially in the plumb line with the center of gravity of the unit, but that by lifting the carrier means, subsequent to the fixing of the unit at the stem by means of the gripping arms, the movable point by overcoming the force of the spring means is caused to participate in the upward swing of the arm to a position, for which the movable point is located substantially in the plumb line with the axle and thereby increases the effective lever of the carrier means so as in the final phase of the cross cutting operation to facilitate the breaking of the tree in the desired felling direction away from the unit.
 2. Suspension device according to claim 1, characterized in that a second arm upwardly inclined relative to the first arm is rigidly connected to the mounting end of said first arm, and that the spring meaNs is mounted between the outer end of said second arm and a holding means on the plate movable in the forward direction of the unit relative to the axle.
 3. Suspension device according to claim 2, characterized in that the spring means comprises at least one tension spring, one rubber belt or the like, and that the holding means is located substantially above the center of gravity of the unit.
 4. Suspension device according to claim 2, characterized in that the spring means comprises at least one compression spring or rubber hollow spring, which with its end remote from the axle abuts an end stop on a rod extending through said spring and with its other end abuts a holding means through which said rod projects and is hinged at its end with the outer end of said second arm via a link.
 5. Suspension device according to claim 1 characterized in that it comprises a stop means preventing at the felling of the tree the movable point from moving with its plumb line past the axle.
 6. Suspension device according to claim 5, characterized in that the stop means comprises a hinged link or chain engaging between a forward point on the unit, preferably near the holder, and a place on the first arm, preferably near the movable point. 